As you read this page, the light you see from your screen is being condensed and focused by your eyes by a concentrated solution of crystallins proteins. These functions on the lens require its absolute transparency, and it is this characteristic that is generated by crystallins. Early on in development, the cells that make up the lenses of our eyes fill themselves with these proteins and then eject their nuclei and mitochondria, becoming a long solution of protein. We rely on these proteins to see for the rest of our lives.
Crystallins may be the proteins with the most deceptive name, for they are charcterised for their inability to form crystals. Since the eye lens must contain a highly concentrated solution, it must avoid the formation of crystals since these would scatter the light that enters the lens and make it opaque. So that crystals are indeed not formed, our lens mixes together many different crystallins.
There are two main classes of crystallins. Most is known about alpha-crystallin, which has chaperone-like properties including the ability to prevent the precipitation of denatured proteins and to increase cellular tolerance to stress. It has been suggested that these functions are important for the maintenance of lens transparency and the prevention of cataracts. Indeed, alpha-crystallin mutations show an association with cataract formation.
‘Til next time…